Cheddar cheese is traditional for making a grilled cheese sandwich, but we also made sandwiches with swiss, camembert, and blue cheese. Mixing 2 or 3 cheeses together makes an interesting grilled cheese sandwich.
We also used different breads, like raisin bread. You can also add other things like ham or sliced apples. Olive oil makes a good substitution for the butter. Great quick lunch or snack.